Impact modification of poly(caprolactam) by copolymerization with a low molecular weight polybutadiene

Caprolactam and a reactive, low molecular weight polybutadiene were polymerized in an autoclave, followed by post-condensation in the solid state. The rubber concentration was varied (0–30 wt%). The morphology of the reaction products was studied by transmission electron microscopy. In the materials with 10 and 20 wt% polybutadiene, large spherical polybutadiene-rich domains with nylon sub-inclusions were observed. The 30 wt% polybutadiene product was shown to have a co-continuous structure. The moduli of the materials decrease rapidly with rubber content and only the material with the highest polybutadiene content had a high notched Izod impact strength

Impact behaviour of nylon-rubber blends: 4. Effect of the coupling agent, maleic anhydride

Blends of 90 wt% nylon-6 and 10 wt% EPDM (ethylene propylene diene monomer) rubber were prepared. The rubber was grafted with various amounts of maleic anhydride (MA) with the aid of a peroxide. The initial moduli and the melt viscosities of the rubbers were only a little affected by the MA and peroxide concentrations. The effect of MA concentration on the blending process and the impact behaviour was studied. The interfacial layer was investigated using infra-red spectroscopy and elemental analysis. The MA grafted onto the rubber was found to react with the nylon during the blending process. With the MA-grafted rubbers, a much finer dispersion could be obtained. However, the concentration of the coupling agent, within the range 0.13 to 0.89 wt% grafted onto the rubber, has hardly any influence on either the dispersion process or the impact behaviour of the blends

Impact behaviour of nylon-rubber blends: 6. Influence of structure on voiding processes; toughening mechanism

Dilatometry tests were performed on nylon-rubber blends with various rubber concentrations, particle sizes and types of impact modifier. Whereas rubber concentration and particle size do not affect the onset of voiding in the blends during a tensile test, the type of elastomer used has a considerable effect. A correlation exists between the stress at which the rubber particles cavitate (or detach from the matrix) in the tensile test and the impact behaviour of the blend. A toughening mechanism is proposed in which the cavitation stress of the rubber and the interparticle spacing play crucial roles

Ductile transition in nylon-rubber blends: influence of water

On nylon 6 and nylon 6/EPDM blends the influence of water on the glass transition temperature, mechanical properties, and the ductile transition temperature was studied. Blends of 10% and 20% were prepared with a particle size of 0.3 µm and the tensile properties, flexural moduli, torsion moduli, and notched izod impact strength were studied as functions of water concentration. The ductile transition temperature in polyamides can be lowered by plasticizing the nylon and by a rubber particle-induced process; both processes show some synergistic effects

Impact behaviour of nylon-rubber blends: 5. Influence of the mechanical properties of the elastomer

Blends of 90wt% nylon-6 and 10wt% impact modifier were prepared. As impact modifiers were used: EPDM (ethylene propylene diene monomer) rubber, EPM (ethylene propylene monomer) rubber, polyethylene, four poly(ether esters) and some commercial impact modifers. EPDM, EPM and polyethylene were functionalized with maleic anhydride. The mechanical properties of the impact modifiers were tested with both a torsion pendulum test and a tensile test. The notched impact strength of the blends was measured as a function of temperature. The relation between the mechanical properties of the elastomer and the impact behaviour of the elastomer-modified nylon-6 was studied while taking into account the effect of the rubber particle size. The type of impact modifier was found to have a strong effect on the impact behaviour of the blend. The rubber particles do not toughen nylon-6 by acting as stress concentrators

Brittle-tough transition in nylon-rubber blends: effect of rubber concentration and particle size

Blends of nylon-6 and EPDM-rubber were prepared with various rubber contents (0–20 wt%) and particle sizes (0.3–1.6 μm). The effects of rubber concentration and particle size on the tensile modulus, torsion modulus, yield stress and notched impact strength of the blends were studied. Blend structures and fracture surfaces were investigated by scanning electron microscopy. Rubber particles induce a sharp brittle-tough transition which is independent of the glass transition temperature of the nylon matrix. The brittle-tough transition temperature for notched Izod impact tests shifts to lower values when the rubber content is increased or the particle size is decreased. A correlation was found between the brittle-tough temperature and the interparticle distance. Two deformation modes were observed: voiding and shear yielding. Particle size and interfacial adhesion affect neither the yield stress nor the modulus of the blends